Seat Having A Backrest Which Can Be Adjusted To Form A Precurved Deformation

ABSTRACT

The backrest which is designed for a seat can be adjusted to form a precurved deformation. The backrest has a rest support ( 40 ) having a link chain ( 41 ) comprising a large number of links ( 410,411 ) which are interconnected such that they can move in relation to each other. A flexible actuating element ( 47 ) with a fixed length extends from an upper fixing point ( 415 ), which is provided on one of the links ( 410,411 ) in the upper region of the rest support ( 40 ), along the rest support ( 40 ) to a lower fixing point. Each link ( 410,411 ) has a driver ( 412 ) which engages in the link ( 411 ) arranged beneath it. The flexible actuating element ( 47 ) is embedded in a guide ( 46 ) which is provided on the rest support ( 40 ) and which extends from close to the upper fixing point ( 415 ) to an intermediate space which is situated in front of the lower fixing point. Means ( 43,45 ) for displacing the actuating element ( 47 ) in the guide ( 46 ) and precurving the upper fixing point ( 415 ) with an associated link ( 410,411 ) are provided for the purpose of adjusting the backrest. The driver ( 412 ) of the link ( 410,411 ) which is associated with the upper fixing point ( 415 ) and engages in the next link ( 411 ) which is arranged beneath it is intended to move this next link ( 411 ) to the precurved position. The further drivers ( 412 ) within the link chain ( 41 ) serve in each case to move the coupled link ( 411 ) to the precurved position.

FIELD OF APPLICATION OF THE INVENTION

The present invention relates to a seat comprising a backrest which may be adjusted into a precurved deformation. The backrest has a backrest support with a link chain consisting of a plurality of movably interconnected links. The invention relates, in particular, to vehicle seats and chairs, including office swivel chairs, which may be adjusted in the seat height thereof, wherein a synchronous adjustment of the seat inclination follows the inclination of the backrest. In a typical design, a spring, preferably a gas spring, for adjusting the seat height is arranged between the chair lower frame and the mechanism resting thereon. In one particular embodiment, as a result of the load effect the backrest fastened to the mechanism adopts a successively precurved deformation counter to the load effect from a zero position which in principle is vertical to a maximum rearwardly inclined position.

PRIOR ART

A seat shell is disclosed in DE 36 04 534 A1, transversely extending resilient areas being provided in the back part thereof for flexibility when a user leans back into the seat. The resilient areas are formed by transverse ribs bridged relative to one another by film hinges. Stop elements are located between the transverse ribs, said stop elements colliding when bent back to the maximum permitted extent.

U.S. Pat. No. 5,328,245 discloses a backrest having a plurality of elements which are, in principle, horizontally displaceable relative to one another and which are adapted in profile to the contour of a user leaning against said backrest. All the elements may be locked in position after adapting the profile to the individual user. The object of adapting the backrest to the back profile of a user by a plurality of chambers extending transversely over the flexible plastics back and superimposed over one another is achieved in DE 10 2004 032 765 B4. The chambers may be pumped up with air to a variable extent so that they are deformed to different degrees of flexibility in order to be adapted to the back of the individual user.

The subject-matter of DE 42 16 159 A1 is a chair, the backrest thereof when inclined to the rear synchronously driving the seat which is lowered in the rear region. The backrest is subdivided at least twice, namely into an upper and a lower part, wherein the parts are connected together in an articulated manner via horizontal axes. To the rear of the backrest, an upwardly protruding supporting arm is present, from which in the pelvic region an articulated transverse lever extends to the backrest and is also articulated at that point. When inclined to the rear, the backrest is lowered in its entirety, and at the same time the seat is slightly lowered in the front region and to a greater extent in the rear region. Due to the displacement between the backrest and the supporting arm, the transverse lever reaches the horizontal position and thus pushes the lower part of the backrest against the user.

The chair according to DE 195 02 485 C2 has a base positioned on a lower frame, said base extending from below the seat as far as half way up the backrest. The base and seat are connected together by a first lever articulated on both sides on the front region thereof. In the upwardly curved part of the base is located a stirrup which is displaceable in an arcuate groove, which is connected in an articulated manner to the rear region of the seat via a second lever articulated to the stirrup. A third lever extends to the backrest from the upper stirrup end with an articulation on both sides. In the writing position, the user exerts a load on the front seat region, which is thus lowered and pulls the stirrup upwards via the second lever and, as a result, also moves the backrest upward and toward the user. If the user displaces his/her weight onto the rear seat region, the backrest is synchronously moved downward when the seat is lowered.

The chair according to WO 2007/038 879 A1 has a lower frame positioned on the floor, a mechanism positioned on the lower frame, a seat positioned on the mechanism and a backrest fastened to the mechanism. The backrest has a backrest frame which bears a resiliently deformable backrest part having a back plate. The back plate has a back part to which a headrest attachment is connected. The backrest is able to be pivoted about a first rotational axis from a zero position which is upright in principle, as far as an inclined position facing to the rear. The movements of the seat and backrest are synchronized with one another. With resilient deformation of the back part into a free intermediate space relative to the backrest frame, by the action of a force in the direction of the inclined position with, in principle, a concave tendency relative to the back of the user, means are provided for an opposing lifting of the shoulder region as a transition area of the back part relative to the headrest attachment and of the headrest attachment. Said means are substantially in each case a support articulated on both sides between the backrest frame and the back plate.

U.S. Pat. No. 6,986,549 B2 finally discloses a backrest support which initially consists of two curved S-shaped flexible tracks coming together at the upper ends in a V-shape. The tracks are subdivided into a plurality of portions connected together by film hinges. An opening is provided in the region of each film hinge, and between the opposing openings in each case a rigid rib is fastened which is pivotable in the vertical plane, said rib holding the two tracks spaced apart from one another. Below the seat, a plurality of traction cables are tensioned and which in each case are fastened by the front track through an opening transversely to the rear track on the next highest rib. When inclining the backrest support to the rear, due to a cable extension which is not available, the connection of the traction cable together with the rib and adjacent portions of the tracks are precurved in the direction of the user.

OBJECT OF THE INVENTION

Based on the hitherto known prior art, the object of the invention is to propose a seat with perfect ergonomic function. In particular, when the backrest is located in the inclined position moved to the rear, the support of the shoulder region and head of the user is improved.

It should be taken into consideration here that the seat may also be provided with a so-called synchronous mechanism, in order to produce an adequate adjustment of the inclination of the seat with an adjustment of the inclination of the backrest, and fulfill the functions of a height-adjustable office swivel chair.

OVERVIEW OF THE INVENTION

The backrest designed for a seat is able to be adjusted into a precurved deformation. The backrest has a backrest support with a link chain consisting of a plurality of movably interconnected links. A flexible actuating element of fixed length extends from an upper fixed point which is provided on one of the links in the upper region of the backrest support, along the backrest support to a lower fixed point. Each link has a drive element which engages in the link arranged thereunder. The flexible actuating element is embedded in a guide provided on the backrest support, said guide extending from the vicinity of the upper fixed point to an intermediate space mounted in front of the lower fixed point. For adjusting the backrest, means are provided for displacing the actuating element in the guide and precurving the upper fixed point with the associated link. The drive element of the link associated with the upper fixed point, which engages in the next link arranged thereunder, is intended for moving said next link into the precurved position. The further drive elements inside the link chain in each case serve for moving the coupled link into the precurved position.

The following features relate to specific embodiments of the invention:

The inclination of the backrest is able to be adjusted, wherein:

-   a) by the load effect, the backrest adopts a successive precurved     deformation counter to the load effect, from a zero position, which     in principle is vertical, to a maximum rearwardly facing inclined     position; -   b) the backrest has a restoring spring for adjusting the backrest     into the zero position in the absence of the load effect; -   c) a freely floating longitudinal portion of the actuating element     extends through the intermediate space; and -   d) when adjusting the backrest toward the inclined position the     means are provided for the longitudinal alteration of the     longitudinal portion with the equivalent displacement of the     actuating element in the guide and precurving of the upper fixed     point with the associated link.

When adjusting the backrest toward the inclined position, the means for longitudinal alteration of the longitudinal portion with equivalent displacement of the actuating element in the guide generate a shortening of the longitudinal portion with equivalent insertion of the actuating element into the guide and precurving of the upper fixed point with the associated link. The actuating element takes the form of a leaf spring, a resilient rod or a Bowden cable or a cord.

The means comprise:

-   a) a backrest connector which, on the one hand, is connected to the     link chain as a component of the backrest support and, on the other     hand, is articulated on a first rotational axis present on the     mechanism; and -   b) an actuating arrangement which has the lower fixed point and is     connected to the backrest connector.

The actuating arrangement:

-   a) is connected to the backrest connector on a connection axis; -   b) has means for adjusting the ratio of the precurved deformation of     the link chain effected by the maximum inclined position; and -   c) has means for preadjusting a precurved deformation of the link     chain in the zero position.

The actuating arrangement consists of:

-   a) a second axle rod extending in the connection axis, which rests     in bearings on the backrest connector; -   b) two bearing elements which are guided on the connection axis; -   c) a base positioned between the two bearing elements, said base     being connected to a fixed seating component and having a first axle     rod, through which a base axis extends and which is guided on both     sides in each case in a first slot in the two bearing elements; and -   d) a receiver unit, on which the lower fixed point is located and     which has a third axle rod, through which a connection axis extends     and which is articulated on both sides on the two bearing elements.

For adjusting the position of the lower fixed point:

-   a) each of the two bearing elements in each case has a second slot     in which the positioning of the third axle rod may be adjusted;     and/or -   b) the receiver unit is adjustable per se, for example by     lengthening and/or shortening in relation to the third axle rod.

Alternatively, the actuating arrangement in a second variant consists of:

-   a) a receiver unit, wherein: -   aa) the lower fixed point is located on the receiver unit; -   ab) the receiver unit has a slot in which an axle pin extending on     the connection axis is guided in a manner which is fixed in terms of     rotation and displaceable; and -   ac) a projection extends from the receiver unit; and -   b) an adjusting unit, wherein: -   ba) the adjusting unit is fastened to a seat support associated with     the seat, and is preferably articulated on a rear axis arranged on     the seat support; -   bb) the adjusting unit has an impact element, the position thereof     being able to be varied by an actuating member; and -   bc) the impact element strikes the projection in order to position     the receiver unit guided on the axle pin, according to the     adjustment on the adjusting unit.

The projection bears against the impact element with a wedge surface and is moved downward on the impact element, when adjusting the backrest toward the inclined position.

The link chain is terminated at the very top by a top link, in which the upper fixed point is provided and to which a first chain link is adjoined, followed by further chain links. A bridging link adjoins the final bottom chain link, which is rigidly connected to the backrest connector or is configured integrally with the backrest connector. The link chain of the backrest support may be formed as far as the shoulder region of the user or, lengthened in height, beyond a top part.

The movable chain links between the links of the link chain and preferably also between the final bottom chain link and the bridging link are formed by hinges in the form of elements positively connected together or film hinges. The link chain is provided on the side remote from the seat part with rear stops which, remote from the seat part, block the link chain and bridging link from bending to the rear. The link chain may be provided on the side facing the seat part with front stops, which block a precurved deformation counter to the load effect, facing the seat part, beyond a maximum defined mass.

The mechanism positioned on a lower frame:

-   a) when adjusting the backrest between the zero position and the     inclined position, serves for the synchronous movement of the seat     part between a zero inclination and a maximum inclination; -   b) comprises a base part, in principle fixedly positioned on the     lower frame, through which the first rotational axis, which is fixed     in principle, extends; -   c) comprises a seat support supporting the seat part through which a     second rotational axis extends, to which connectors are articulated,     on the one hand, which are articulated, on the other hand, to the     first rotational axis; and -   d) has a third rotational axis extending through the base part, to     which the seat support is articulated.

The backrest connector is fastened to the connectors. The backrest connector is of two-arm configuration and both arms have in each case a molded part at the ends facing the connectors, said molded part being intended for fastening to the respectively associated connector. At least several links of the link chain and optionally also the bridging link are provided with upholstery supports, which serve for supporting an upholstered part present on the backrest. The upholstery supports are fastened by means of connecting links to the respective link or extend integrally from the respective link.

The link chain:

-   a) is an integral plastics molded part; or -   b) is an integral plastics molded part with the upholstery supports;     or -   c) is an integral plastics molded part with the upholstery supports     and the bridging link; or -   d) is an integral plastics molded part with the upholstery supports     and the bridging link and the backrest connector.     The restoring spring—for adjusting the backrest into the zero     position when there is no load effect—is an additional function of     the actuating element and a separate traction element may be fixed     to the backrest support for reinforcing the restoring function of     the actuating element. In this case, the traction element is fixed     between the top link and the bridging link, preferably on the rear     side of the backrest support remote from the user. Alternatively,     the restoring spring is formed by the hinges between the links     and/or by the additional function of the actuating element and/or     the separate traction element.

On the backrest support within the link chain:

-   a) various areas of curvature are formed with a variable precurved     deformation with, in principle, variable radii of curvature; and/or -   b) different areas of rigidity are formed with variable deformation     resistance; and -   c) the various areas of curvature with the different areas of     rigidity may be configured to be superimposed on one another.

On the backrest support inside the link chain, in a particular embodiment:

-   a) in the upper region thereof in relation to the lower region a     greater precurved deformation is provided in order to provide to the     user leaning into the seat, upwards from the shoulder, with a     support oriented further toward the user, which may be achieved by     different dimensioning and/or variable use of material inside the     link chain; and -   b) the lumbar region in relation to the remaining link chain is     formed with a greater deformation resistance, in order to support     the user more firmly thereby in said body region.

A spring, preferably a gas spring, is arranged between the lower frame and the mechanism for adjusting the seat height. The seat is configured as a swivel chair. The base of the adapter arrangement is fastened to the base part of the mechanism or to an extending piston rod of the gas spring.

The backrest support is provided on the side facing the user with an upholstered part, which has a lumbar region and at the top may have a top part. A height-adjustable support element is provided in the lumbar region of the upholstered part and the top part is vertically displaceable.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the drawings:

FIG. 1A—shows a chair according to the invention in the form of an office swivel chair with a backrest extended by a top part, in the upright zero position, in a perspective front view;

FIG. 1B—shows the chair according to FIG. 1A with the visible backrest support of the first variant in a perspective rear view;

FIG. 1C—shows the chair according to FIG. 1A in a side view;

FIG. 1D—shows the chair according to FIG. 1C without the top part;

FIG. 2A—shows the chair according to FIG. 1A in the maximum inclined position in a perspective front view;

FIG. 2B—shows the chair according to FIG. 2A in a perspective rear view;

FIG. 2C—shows the chair according to FIG. 2A in side view;

FIG. 2D—shows the chair according to FIG. 2C without the top part;

FIG. 3A—shows the mechanism of FIG. 1A in a perspective front view from above;

FIG. 3B—shows the mechanism according to FIG. 3A in a side view;

FIG. 3C—shows the mechanism according to FIG. 3A with the seat in position, in a perspective front view from below;

FIG. 3D—shows the construction according to FIG. 3C in a perspective rear view from below;

FIG. 4A—shows the backrest support of FIG. 1B, without the upholstery support in the upright zero position, in a perspective front view;

FIG. 4B—shows the construction according to FIG. 4A in a perspective rear view from below;

FIG. 4C—shows the construction according to FIG. 4A as a basic sectional view;

FIG. 4D—shows the enlarged detail X1 of FIG. 4C;

FIG. 4E—shows the enlarged detail X2 of FIG. 4C;

FIG. 5A—shows the backrest support according to FIG. 4A, completed with the upholstery supports and upholstery to form a backrest, in the upright zero position, in a perspective rear view;

FIG. 5B—shows the backrest according to FIG. 5A in a perspective rear view from below;

FIG. 5C—shows the backrest according to FIG. 5A in a perspective front view;

FIG. 5D—shows the backrest according to FIG. 5A with the pushing element as a basic sectional view;

FIG. 6A—shows the construction according to FIG. 4A with the pushing element, in a perspective exploded view;

FIG. 6B—shows the enlarged detail X5 of FIG. 6A;

FIG. 6C—shows the enlarged detail X6 of FIG. 6A;

FIG. 7A—shows the construction according to FIG. 4A in the maximum inclined position in a perspective front view;

FIG. 7B—shows the construction according to FIG. 7A in a perspective rear view from below;

FIG. 7C—shows the construction according to FIG. 7A as a basic sectional view;

FIG. 7D—shows the enlarged detail X3 of FIG. 7C;

FIG. 7E—shows the enlarged detail X4 of FIG. 7C;

FIG. 8A—shows the base part of the mechanism positioned on the lower frame, with the fittings, connectors, backrest connector, actuating arrangement and raised seat support in a perspective plan view;

FIG. 8B—shows the construction according to FIG. 8A in a perspective view from below;

FIG. 8C—shows the construction according to FIG. 8A with the seat support positioned on the base part, in a perspective plan view;

FIG. 9A—shows the assembly consisting of the mechanism, backrest connector, molded parts and actuating arrangement in a first setting, in the zero position, as a basic view;

FIG. 9B—shows the assembly according to FIG. 9A in the maximum inclined position;

FIG. 10A—shows the assembly according to FIG. 9A with the actuating arrangement in a second setting, in the zero position;

FIG. 10B—shows the assembly according to FIG. 10A in the maximum inclined position;

FIG. 11A—shows the assembly according to FIG. 9A with the actuating arrangement in a third setting in the zero position;

FIG. 11B—shows the assembly according to FIG. 11A in the maximum inclined position;

FIG. 12A—shows the assembly according to FIG. 9A with the actuating arrangement in a fourth setting in the zero position;

FIG. 12B—shows the assembly according to FIG. 12A, in the maximum inclined position;

FIG. 13A—shows a backrest support of the second variant in the upright zero position in a perspective rear view;

FIG. 13B—shows the link chain and bridging link of FIG. 13A in the upright zero position in a perspective front view;

FIG. 13C—shows the construction according to FIG. 13A in the upright zero position as a basic sectional view;

FIG. 14A—shows the construction according to FIG. 13B in the maximum inclined position in a perspective rear view;

FIG. 14B—shows the construction according to FIG. 14A in the maximum inclined position in a perspective front view;

FIG. 14C—shows the construction according to FIG. 14A in the maximum inclined position as a basic sectional view;

FIG. 15A—shows the construction according to FIG. 9A with an actuating arrangement of the second variant and the actuating element attached thereto with a guide, in the zero position, as a basic sectional view;

FIG. 15B—shows the construction according to FIG. 15A in a perspective view;

FIG. 15C—shows the enlarged detail X7 of FIG. 15A;

FIG. 15D—shows the construction according to FIG. 15A in the maximum inclined position as a basic sectional view; and

FIG. 15E—shows the enlarged detail X8 of FIG. 15D.

EXEMPLARY EMBODIMENT

With reference to the accompanying drawings, an exemplary embodiment of the seat according to the invention is described in detail hereinafter, with alternative designs of the backrest and the actuating arrangement present thereon.

The following statement applies to the entire remaining description. If reference numerals are contained in a figure for the purpose of illustrative clarity, but not explained in the immediately associated text of the description, reference is made to where said reference numerals are mentioned in the previous description of the figures. For the sake of clarity, a repeated description of components in the following figures is generally dispensed with, provided it may be identified clearly in terms of illustration that the components are “recurring” components.

FIGS. 1A to 1D

The seat shown in the form of an office swivel chair consists of the lower frame 1 positioned on the floor, the mechanism 2 resting thereon, on which the seat part 3 is mounted, as well as a backrest 4 which in a comfortable design has a top part h, and is provided with an upholstered part 49. Typically, the lower frame 1 initially has a foot 10—for example a 5-arm star-shaped foot—which rests on floor elements 14, preferably casters. For adjusting the level of the seat part 3 and at the same time for the suspension, a gas spring 12 in a vertical tube 11 is vertically inserted centrally into the foot 10, which bears the mechanism 2. The structure of the backrest 4 consists of the backrest support 40—in this case in a first variant—the upholstery support 48 and the upholstered part 49 resting thereon. The backrest support 40 comprises a link chain 41, the bridging link 42 attached thereto at the bottom, and which is connected to the backrest connector 43, as well as the actuating arrangement 45 in a first variant. By means of connecting links 480, plate-shaped upholstery supports 48 are fastened to the link chain 41 and the bridging link 42, against which the upholstered part 49 bears. The backrest connector 43 leads to the mechanism 2. As a swivel chair, said chair may be pivoted about a vertical rotational axis generally by 360°, and in the unloaded state remains in the zero position, which is enforced by the pretensioning of the spring assembly in the mechanism 2, and is limited by a stop in the direction of forward inclination.

The zero position is defined by the following positions:

-   -   the zero position S₀ of the seat part 3: i.e. the surface of the         seat part 3 is at least in principle horizontal;     -   the zero position R₀ of the backrest support 40: i.e. the link         chain 41 supporting the user and the bridging link 42 are in         principle vertical and thus complement the upright seating         position of a user.

The first rotational axis D1, which is fixed in principle, the second rotational axis D2 which is pivotable about the first rotational axis D1, as well as the third rotational axis D3, which is also fixed in principle, extend through the mechanism 2. Initially also visible are the fourth rotational axis D4 and the fifth rotational axis D5 which extend through the actuating arrangement 45.

FIGS. 2A to 2D

Due to the load effect produced by a user on the backrest 4, said backrest is able to move fully into the maximum rearwardly inclined position R_(max). The design of the mechanism 2 as a synchronous mechanism follows the seat part 3 from the previous zero position S₀ into the maximum seat inclination S_(max). According to the invention, here, the backrest 4 with the link chain 41 in the backrest support 40 reaches a precurved deformation counter to the load effect, so that the user leaning into the seat is supported with an upright tendency, in particular in the shoulder and head region, and the user's eyes maintain a virtually horizontal viewing direction.

In the backrest 4, a restoring spring, not shown, is provided, which in the absence of the load effect, effects the adjustment of the backrest 4 with the backrest support 40 into the zero position R₀. The embodiments according to FIGS. 2A-2C are provided with the top part h, whilst in the embodiment according to FIG. 2D, the link chain 41 is shortened and thus does not have a top part h.

FIGS. 3A to 3D

The mechanism 2 is disclosed in the patent publications WO 2005/120291A1 and WO 2007/038879A1, and substantially consists of the base part 20, the seat support 21 positioned thereon and the connectors 22. The base part 20 is fixedly positioned with its opening 200 on the upper end of the extendable piston rod, a gas spring 12 arranged in a vertical tube 11. The two angular connectors 22 are articulated on the first rotational axis D1 which, at the same time, are articulated on the second rotational axis D2 in the bearing recesses 210 in the rear region of the pivotable seat support 21. In the front region, the base part 20 and the seat support 21 are connected together on the third rotational axis D3. On both sides of the seat support 21 in each case extends an armrest connecting piece 24 into which the free end of the support arm of an armrest may be introduced. Additionally, an adjustment connecting piece 25 may be present adjacent to one of the armrest connecting pieces 24, in which an actuating member rests, which when actuated permits the adjustment of the so-called seat depth, by the upholstered plate 30 mounted on the seat support 21, which forms the underside of the seat 3, being released from a blocked position and being displaceable in a limited manner. The conventional height-adjustment lever 26 is present on the mechanism 2 in order to release the piston rod of the gas spring 12 from the blocked position, and thus raise the seat part 3. The blocking lever 27 serves for blocking the mechanism 2, so that the backrest 4 is not able to be moved from the vertical zero position into the inclined position R_(max). Finally, a pretensioning lever 28 is present, which serves to adjust a force to be applied for the adjustment of the backrest 4, on the spring system not shown, associated with the mechanism 2.

FIGS. 4A to 6C

This sequence of figures illustrates the structural design of the complete backrest 4 with the entire backrest support 40, comprising the link chain 41, bridging link 42, backrest connector 43, molded parts 44 and actuating arrangement 45 in the current zero position R₀. The link chain 41, also comprising a top part h, starts at the very top with a top link 410, which is connected by means of a hinge 417 to a first link 411. Further links 411 interlinked by hinges 417, follow said first link 411, wherein the lowest link 411 is connected via a hinge 417 to the immobile bridging link 42. Each link 411 partially contributes to an upper and lower hinge 417. The upper hinge 417 serves for the connection to the link 411 arranged above the relevant link 411 and/or top link 410, and the lower hinge 417 serves for the connection to the link 411 arranged below the relevant link 411 and/or bridging link 42. A hinge 417 in this case consists of a pin in the top link 410 and in the links 411, as well as pin holes in the links 411 and in the bridging link 42.

On the front face, in each case between the links 410,411,42, a front stop 413 is present which defines the maximum possible forward inclined angular position between the links 410,411,42. In any case between the front stops 413, which belong to the top link 410 and the subsequent links 411—namely those links 410,411 which are moved in the inclined position R_(max) into the precurved deformation—in each case an open gap is present, in order to permit the movement of the links 410,411 toward one another counter to the load effect. The connecting links 480 for fastening the upholstered support 48 are mounted on the front stops 413. A rear stop 414 is arranged on the rear face in each case between the links 410,411,42, which prevents the rearwardly inclined angular position between the links 410,411,42, and thus the rear stops 414 abut against one another without gaps. The top link 410 and the adjacent chain-like links 411 in each case have a drive element 412, which from a defined forwardly inclined angular position drives the next link down 411 into a forwardly inclined angular position.

The rear stops 414, with in each case a cover plate 416 mounted inside the link chain 41, enclose a through-hole which together form the upper part of the guide 46 for the actuating element 47. The guide 46 terminates in the top link 410 with an additional cover plate 416 on the upper fixed point 415 as the clamping point for the actuating element 47. From the lowest link 411, the guide 46 merges with the elongated bridging link 42 and extends as far as the guide opening 462 at the lower end of the bridging link 42. The actuating element 47 extends from the upper fixed point 415 through the guide 46, enters a free intermediate space 460 at the guide opening 462 and is gripped on the lower fixed point 458 of a receiver unit 459. Inside the free intermediate space 460 the actuating element 47 extends in a curved path as a freely floating longitudinal portion a.

For fastening the backrest support 40 to the two connectors 22 of the mechanism 2 each of the two arms of the backrest connector 43 on the lower end is provided with a molded part 44, which has the first retaining contour 441 and the second retaining contour 442, in order to dock onto the associated connector 22. The lower part of the bridging link 41 is fitted between the two upwardly oriented arms of the backrest connector 43.

The actuating arrangement 45 is connected to the backrest connector 43 on the fifth rotational axis D5. To this end, in the vicinity of the molded parts 44 on each arm of the backrest connector 43 a bearing element 430 is present in order to receive therein a second axle rod 456, through which the fifth rotational axis D5 extends. The adapter arrangement 45 further consists of:

-   -   two bearing elements 453 configured as angled portions, which         are guided on the fifth rotational axis D5;     -   a base 450 positioned between the two bearing elements 453,         which is connected to the base part 20 of the mechanism 2 or to         the opening 451, comprising the extendable piston rod of the gas         spring 12, and has a first axle rod 452, through which the         fourth rotational axis D4 extends and which on both sides in one         respective first slot 454, is guided into the two bearing         elements 453; and     -   a receiver unit 459, on which the lower fixed point 458 is         located and which has a third axle rod 457, through which a         sixth rotational axis D6 extends and which is articulated on         both sides to the two bearing elements 453.

For adjusting the position of the lower fixed point 458, each of the two bearing elements 453 has one respective second slot 455, in which the positioning of the third axle rod 457 is adjustable. Moreover, the receiver unit 459 is adjustable per se, for example by the lengthening and/or shortening thereof in relation to the third axle rod 457. To this end, the front part of the receiver unit 459—the lower fixed point 458 is located there—may be adjusted by the rear anchor part of the receiver unit 459 connected thereto—the third axle rod 457 is inserted therein—from a very tight joint to a selectable spacing.

In the current upright zero position R₀ of the backrest support 40 and the opposing adjustment of the receiver unit 459, are located—starting from the fixed fourth rotational axis D4—the fifth rotational axis D5 above D4, in relation to the backrest support 40, and the sixth rotational axis D6 in principle vertically above D5. The bearing elements 453 are such that the first slot 454 is virtually horizontally aligned and the second slot 455 is virtually vertically aligned. The actuating arrangement 45 is located in a second setting (see also FIG. 10A), i.e. the sixth rotational axis D6 with the anchor part of the receiver unit 459 plugged thereon is located in the second slot 455 in the lowest position and the front part of the receiver unit 459 is adjusted to be spaced apart from the anchor part.

With the plate-shaped upholstered supports 48 fastened to the connecting links 480 and the upholstered part 49 attached thereto, a complete backrest 4 is produced which extends over the lumbar and shoulder region as well as the lengthened top part h.

FIGS. 7A to 7E

This sequence of figures illustrates the details of the entire backrest support 40 in the maximum inclined position R_(max) now adopted by the load effect on the backrest 4. The assembly of the molded parts 44, backrest connector 43 and bridging link 42 rigidly connected together is inclined to the rear and has entrained the entire link chain 41. By the rearward inclination of the bearing elements 430 on the backrest connector 43, the fifth rotational axis D5 is moved downwards and the bearing elements 453 guided into the first slots 454 on the fourth rotational axis D4 are pulled into the oblique position. Starting from the fixed fourth rotational axis D4, the fifth rotational axis D5 is now below D4, in relation to the backrest support 40, and the sixth rotational axis D6 above D5. The bearing elements 453 are such that the first slot 454 and the second slot 455 are aligned in a V-shape relative to the floor. The actuating arrangement 45 is further located in the second setting, thus the sixth rotational axis D6 with the anchor part of the receiver unit 459 plugged thereon is located in the second slot 455 in the lowest position and the front part of the receiver unit 459 is spaced apart from the anchor part.

Thus by the guide opening 462 and the lower fixed point 458 approaching one another, the intermediate space 460 has been narrowed and the freely floating longitudinal portion a of the actuating element 47 is shortened. By the nature of the flexible actuating element 47, the positioning of the guide opening 462 and the lower fixed point 458 as well as the forced path of the actuating element 47 in the guide 46, at least a substantial component of the shortening of the longitudinal portion a along the guide 46 is pushed against the upper fixed point 415. A deformation curved to the rear between the links 410,411 is excluded by the rear stops 414 striking one another. The rear positioning of the upper fixed point 415 on the top link 410 when the actuating element 47 is lifted promotes merely the forward bending thereof counter to the load effect. The drive element 412 on the top link 410 effects a similarly forwardly oriented bending of the next link 411, which in turn pulls forward the following link 411 by means of the associated drive element 412. Depending on the dimensioning, the precurved deformation only continues to a few adjacent links 411 inside that located in the direction of the bridging link 42, i.e. the links 411 located closer to the bridging link 42, in the lumbar region of the user, are no longer able to be included in the forwardly curved deflection. By different dimensioning inside the link chain 41, in the upper region thereof—substantially above the top part h—a greater precurved deformation may be achieved than downwards in the direction of the bridging link 42 to the lumbar region of the user. Thus the user leaning back into the seat, from the shoulder upwards, experiences a support oriented further toward him/her. Moreover, areas of variable stiffness may be formed inside the link chain 41 so that, for example, the lumbar region on the seat provides to the user leaning against the seat a greater resistance against deformation—i.e. acts harder—and therefore supports the user more firmly in said body region.

FIGS. 8A to 8C

This sequence of figures illustrates as a complement to FIGS. 3A-3D the assembly consisting of the lower frame 1, the base part 20 positioned thereon of the mechanism 2, connectors 22, backrest connector 43, actuating arrangement 45 and the initially still raised seat support 21 (see FIGS. 8A and 8B). The entire backrest support 40 is fastened with its backrest connector 43 to the connectors 22. In this case, the molded parts 44 are preferably screwed to the connectors 22, and the first retaining contours 441 of the molded parts 44 engage behind through-holes, not denoted, on the connectors 22 in the vicinity of the second rotational axis D2. The base 450 of the actuating arrangement 45 is located with its opening 451 on the extending piston rod of the gas spring 12 or could be fastened to the base part 20. When the seat support 21 is positioned on the base part 20 (see FIG. 8C), both are connected together on the second rotational axis D2 and the third rotational axis D3. Typically for a synchronous mechanism 2, the seat support 21 follows a rearward inclination of the backrest support 40 in the direction of the maximum seat inclination S_(max) lowered to the rear. If the seat is to be designed neither as a swivel chair nor able to be adjusted in height, a fastening of the base 450 to a further fixed part of the seat, for example the lower frame 1, is also considered.

FIGS. 9A to 12B

The following four pairs of figures show the actuating arrangement 45 of the first variant in four different settings, namely in each case in the zero position R₀ of the backrest support 40 with associated zero inclination S₀ of the seat support 21 and in the maximum inclined position R_(max) thereof, with associated maximum seat inclination S_(max).

In the first setting (see FIGS. 9A and 9B), the sixth rotational axis D6 is located with the anchor part of the receiver unit 459 plugged thereon in the second slot 455 in the lowest position. Thus a low ratio is present of the precurved deformation of the link chain 41 effected by the maximum inclined position R_(max). When adjusting the front part of the receiver unit 459 without spacing from the anchor part, as a preadjustment in the zero position R₀ of the backrest support 40 with associated zero inclination S₀ of the seat support 21, no or only minimal precurved deformation of the link chain 41 results. When changing from the zero position R₀/zero inclination S₀ into the maximum inclined position R_(max)/seat inclination S_(max), the link chain 41 is subjected to the smallest precurved deformation in relation to its initial position.

In the second setting (see FIGS. 10A and 10B) the sixth rotational axis D6 with the plugged-on anchor part of the receiver unit 459 is located in the second slot 455, also in the lowest position, but the front part of the receiver unit 459 is spaced apart from the anchor part. When moving from the zero position R₀/zero inclination S₀, into the maximum inclined position R_(max)/seat inclination S_(max), the ratio of the precurved deformation of the link chain 41 effected by the maximum inclined position R_(max), therefore, remains unaltered relative to the first setting. However, a greater precurved deformation of the link chain 41 already results as a preadjustment in the zero position R₀ of the backrest support 40 with the associated zero inclination S₀ of the seat support 21. In the maximum inclined position R_(max)/seat inclination S_(max)—in comparison with the first setting—a more extensive precurved deformation of the link chain 41 thus results.

In the third setting (see FIGS. 11A and 11B) the sixth rotational axis D6 with the anchor part of the receiver unit 459 plugged thereon is now located in the second slot 455 in the highest position and the front part of the receiver unit 459 is adjusted so as not to be spaced apart from the anchor part. Thus a high ratio of the precurved deformation of the link chain 41 effected by the maximum inclined position R_(max) is selected. The preadjustment of the precurved deformation of the link chain 41 in the zero position R₀ of the backrest support 40 with the associated zero inclination S₀ of the seat support 21 corresponds to the first setting. Due to the higher ratio when reaching the maximum inclined position R_(max)/seat inclination S_(max)—in comparison with the first setting—a more extensive precurved deformation of the link chain 41 is produced.

In the fourth setting. (see FIGS. 12A and 12B) the sixth rotational axis D6 is located in the second slot 455 in the highest position and the front part of the receiver unit 459 is additionally adjusted so as to be spaced apart from the anchor part. Thus a high ratio according to the third setting is selected and at the same time a preadjustment according to the second setting so that in the maximum inclined position R_(max)/seat inclination S_(max), the greatest precurved deformation of the link chain 41 results.

FIGS. 13A to 13C

In this case, a backrest support 40 of the second variant is shown in the current upright zero position R₀. The link chain 41 is configured as an integral plastics molded part which starts at the very top with a top link 410, followed by successive links 411. On the final bottom link 411, an integral or joined-on bridging link 42 is adjoined, which is rigidly connected to the backrest connector 43, or may be configured integrally with the backrest connector 43. By way of example, the link chain 41 is extended in height and configured with a top part h. The movable linkages between the links 410,411 and preferably also between the lowest final link 411 and the bridging link 42 are formed by hinges 417—for example film hinges. In the top link 410, the upper fixed point 415 is provided from which the guide 46 extends to the guide opening 462 on the bridging link 42.

On the side remote from the seat part 3, rear stops 414 are provided which block to the rear a bending of the link chain 41 at the transition to the bridging link 42, remote from the seat part 3. The front stop 413 present on the link chain 41 on the backrest support 40 of the first variant on the side facing the seat part 3—in order to block a precurved deformation counter to the load effect, i.e. facing the seat part 3, beyond a maximum defined mass—are not necessary on the backrest support 40 of the second variant.

The upholstery supports 48 may extend integrally from the respective link 410,411,42. The guide 46 for the longitudinally displaceable embedding of the actuating element 47—from the upper fixed point 415 through the top link 410, the entire link chain 41 and through the bridging link 42 to the guide opening 462—is designed in such a manner and the actuating element 47 is such that when pushed upwards, slippage by the deviation of the actuating element 47 is avoided.

Each link 410,411 has in turn a drive element 412, which engages in the next link 411 arranged thereunder, in order to pull said link therewith into the precurved deformation. Whilst the drive elements 412 in the backrest support 40 of the first variant are formed from interlocking curved contours with an end stop, the drive elements 412 in the second variant consist of a hook element which pulls to the front said next link 411 inside a cutout in the next link 411 with increasing precurved deformation of the preceding link 410,411. The design and function of the actuating arrangement 45 in the first variant thereof are unaltered.

The restoring spring which is required for adjusting the backrest support 40 and the entire backrest 4 into the zero position R₀ when there is no load effect, may be formed advantageously by the hinges 417 between the links 411. For example, an elastomer with its dimensionally stable and resilient characteristics is suitable for this purpose and a two-component injection-molding method for producing the backrest support 40 may be used efficiently. Alternatively, when there is no load effect, the actuating element 47 effects the adjustment of the backrest support 40 and the entire backrest 4 into the zero position R₀. In this case, the restoring effect of the actuating element 47 may be reinforced by an additional resilient tractive element. Said tractive element is fixed between the top link 410 and the bridging link 42, preferably on the rear face of the backrest support 40 remote from the user.

As set forth in the sequence of FIGS. 7A-7E with the backrest support 40 of the first variant, it may also be provided in the backrest support 40 of the second variant, to achieve a greater precurved deformation inside the link chain 41 in the upper region thereof—substantially above the top part h—whereas this reduces towards the bridging link 42. To this end, different dimensioning and/or variable use of material inside the link chain 41 is conceivable. In this manner, the user leaning back into the seat, from the shoulder upward, experiences an ergonomically advantageous support oriented further towards him/her, partially opposing the user. At the same time, areas of different rigidity may also be configured inside the link chain 41 of the backrest support 40 of the second variant in order, for example in the lumbar region, to establish a greater deformation resistance on the seat and to support the user more firmly in this body region. Also, when applied to the backrest support 40 of the first variant, within the link chain 41 different areas of curvature with variable precurved deformation—effectively different radii of curvature—and superimposed by curved areas, thus form different areas of stiffness with variable deformation resistance.

FIGS. 14A to 14C

In the maximum inclined position R_(max), the top link 410 and at least the immediately following links 411 of the link chain 41 adopt their precurved deformation counter to the load effect. The actuating element 47 acting on the upper fixed point 415 advancing toward the top link 410 with its drive element 412 has pulled the adjacent link 411, the drive element 412 thereof moving the next link 411 in the same direction. Depending on the dimensioning on the seat, this sequence in the link chain 41 accordingly continues a considerable way in the direction of the bridging link 42. With the precurved deformation between the links 410,411, the gap spacings between the rear stops 414 open up.

FIGS. 15A to 15E

This sequence of figures relates to the use of an actuating arrangement 45′ of the second variant for the backrest support 40 of the first variant according to FIGS. 1A-2C and 4A-7D or the backrest support 40 of the second variant according to FIGS. 13A-14C. The receiver unit 459 on which the lower fixed point 458 for anchoring the actuating element 47 is located, is now in one piece and has a slot 51 for receiving an axle pin 50 which is longitudinally displaceable but fixed in terms of rotation in the slot 51. The axle pin 50 extends on the connection axis D5, and rests in the bearing elements 430 on the backrest connector 43. A projection 52 with a wedge-shaped tip extends from the receiver element 459 to the seat support 21, said tip being slidably applied to an impact element 61 of an adjusting unit 6. From the fixed point 458, the actuating element 47 with its portion a passes through the intermediate space 460, penetrates into the lower guide opening 462 of the guide 46, and extends inside the guide 46 to the upper fixed point 415. The bridging link 42 is received unaltered by the backrest connector 43. Apart from the impact element 61, the adjusting unit 6 has the actuating member 62 which is supported on the stop 211 present on the seat support 21 and, for example, is configured as a screw. The adjusting unit 6 is articulated on the rear axis D7. With a movable or resilient configuration of the impact element 61, the articulation on the rear axis D7 might be dispensed with and replaced by fastening to the rear to the seat support 21. With a deeper insertion of the actuating member 62 into the impact element 61, for example by screwing-in, the impact element is moved towards the receiver unit 459, and said receiver unit is thus pushed on the connection axis D5 with further insertion of the actuating element 47 into the guide 46. This effects a thrust onto the upper fixed point 415 on the top link 410, so that the link chain 41 is forced into a further precurved deformation.

FIGS. 15A to 15C

In contrast, the backrest support 40 and the entire backrest 4 are located in the zero position R₀, and with the current adjustment on the actuating member 62, the axle pin 50 is located to a maximum extent to the left in the slot 51 of the receiver unit 459. The seat support 21 with the mechanism 2 present here, with a synchronous movement sequence between the backrest 4 and the seat part 3, currently adopts the zero inclination S₀.

FIGS. 15D and 15E

When moving the backrest 4 into the maximum rearwardly facing inclined position R_(max), the backrest connector 43 is lowered and at the same time drives the receiver unit 459. At the same time, the projection 52 moves downwards on the obliquely extending impact element 61, and as a result pushes the receiver unit 459 on the axle pin 50 in the direction of the lower guide opening 462, so that the actuating element 47 in the guide 46 is pushed forward against the upper fixed point 415 and the link chain 41 thus successively achieves a greater precurved deformation. The receiver unit 459 moves inside the slot 51 to the left via the axle pin 50. By means of the mechanism 2 with synchronization between the backrest 4 and the seat part 3, the seat support 21 is lowered in the inclined position R_(max) via the fixed first rotational axis D1 and via the movable rotational axes D2,D3 to the rear with the adjusting unit 6. 

1. A seat having a backrest (4), wherein: a) the backrest (4) is able to be adjusted into a precurved deformation; and b) the backrest (4) has a backrest support (40) with a link chain (41) consisting of a plurality of movably interconnected links (410,411), characterized in that c) a flexible actuating element (47) of fixed length extends from an upper fixed point (415) which is provided on one of the links (410,411) in the upper region of the backrest support (40), along the backrest support (40) to a lower fixed point (458); d) each link (410,411) has a drive element (412) which engages in the link (411) arranged thereunder; e) the flexible actuating element (47) is embedded in a guide (46) provided on the backrest support (40), said guide extending from the vicinity of the upper fixed point (415) to an intermediate space (460) mounted in front of the lower fixed point (458); and f) for adjusting the backrest (4): fa) means (43,45;43,45′) are provided for displacing the actuating element (47) in the guide (46) and precurving the upper fixed point (415) with the associated link (410,411); fb) the drive element (412) of the link (410,411) associated with the upper fixed point (415), which engages in the next link (411) arranged thereunder, is intended for moving said next link (411) into the precurved position; and fc) the further drive elements (412) inside the link chain (41) in each case serve for moving the coupled link (411) into the precurved position.
 2. The seat as claimed in claim 1, characterized in that the inclination of the backrest (4) is able to be adjusted, wherein: a) by the load effect, the backrest (4) adopts a successive precurved deformation counter to the load effect, from a zero position (R₀), which in principle is vertical, to a maximum rearwardly facing inclined position (R_(max)); b) the backrest (4) has a restoring spring for adjusting the backrest (4) into the zero position (R₀) in the absence of the load effect; c) a freely floating longitudinal portion (a) of the actuating element (47) extends through the intermediate space (460); and d) when adjusting the backrest (4) toward the inclined position (R_(max)) the means (43,45;43,45′) are provided for the longitudinal alteration of the longitudinal portion (a) with the equivalent displacement of the actuating element (47) in the guide (46) and precurving of the upper fixed point (415) with the associated link (410,411).
 3. The seat as claimed in one of claims 1 and 2, characterized in that a) when adjusting the backrest (4) toward the inclined position (R_(max)), the means (43,45;43,45′) for longitudinal alteration of the longitudinal portion (a) with equivalent displacement of the actuating element (47) in the guide (46) generate a shortening of the longitudinal portion (a) with equivalent insertion of the actuating element (47) into the guide (46) and precurving of the upper fixed point (415) with the associated link (410,411); and b) the actuating element (47) takes the form of a leaf spring, a resilient rod or a Bowden cable or a cord.
 4. The seat as claimed in one of claims 1 to 3, characterized in that the means (43,45;43,45′) comprise: a) a backrest connector (43) which, on the one hand, is connected to the link chain (41) as a component of the backrest support (40) and, on the other hand, is articulated on a first rotational axis (D1) present on the mechanism (2); and b) an actuating arrangement (45,45′) which has the lower fixed point (458) and is connected to the backrest connector (43).
 5. The seat as claimed in one of claims 1 to 4, characterized in that the actuating arrangement (45,45′): a) is connected to the backrest connector (43) on a connection axis (D5); b) has means (455,457,459) for adjusting the ratio of the precurved deformation of the link chain (41) effected by the maximum inclined position (R_(max)); and c) has means (459,6) for preadjusting a precurved deformation of the link chain (41) in the zero position (R₀).
 6. The seat as claimed in at least one of claims 1 to 5, characterized in that the actuating arrangement (45) consists of: a) a second axle rod (456) extending in the connection axis (D5), which rests in bearings (430) on the backrest connector (43); b) two bearing elements (453) which are guided on the connection axis (D5); c) a base (450) positioned between the two bearing elements (453), said base being connected to a fixed seating component (1,11,12,20) and having a first axle rod (452), through which a base axis (D4) extends and which is guided on both sides in each case in a first slot (454) in the two bearing elements (453); and d) a receiver unit (459), on which the lower fixed point (458) is located and which has a third axle rod (457), through which a connection axis (D6) extends and which is articulated on both sides on the two bearing elements (453).
 7. The seat as claimed in claim 6, characterized in that for adjusting the position of the lower fixed point (458): a) each of the two bearing elements (453) in each case has a second slot (455) in which the positioning of the third axle rod (457) may be adjusted; and/or b) the receiver unit (459) is adjustable per se, for example by lengthening and/or shortening in relation to the third axle rod (457).
 8. The seat as claimed in at least one of claims 1 to 5, characterized in that the actuating arrangement (45′) consists of: a) a receiver unit (459), wherein: aa) the lower fixed point (458) is located on the receiver unit (459); ab) the receiver unit (459) has a slot (51) in which an axle pin (50) extending on the connection axis (D5) is guided in a manner which is fixed in terms of rotation and displaceable; and ac) a projection (52) extends from the receiver unit (459); and b) an adjusting unit (6), wherein: ba) the adjusting unit (6) is fastened to a seat support (21) associated with the seat, and is preferably articulated on a rear axis (D7) arranged on the seat support (21); bb) the adjusting unit (6) has an impact element (61), the position thereof being able to be varied by an actuating member (62); and bc) the impact element (61) strikes the projection (52) in order to position the receiver unit (459) guided on the axle pin (50), according to the adjustment on the adjusting unit (6); and c) the projection may have a wedge surface which bears against the impact element (61) and is moved downward on the impact element (61) when adjusting the backrest (4) toward the inclined position (R_(max)).
 9. The seat as claimed in one of claims 1 to 8, characterized in that a) the link chain (41) is terminated at the very top by a top link (410), in which the upper fixed point (415) is provided and to which a first chain link (411) is adjoined, followed by further chain links (411); b) a bridging link (42) adjoins the final bottom chain link (411), which is rigidly connected to the backrest connector (43) or is configured integrally with the backrest connector (43); and c) the link chain (41) of the backrest support (40) may be formed as far as the shoulder region of the user or, lengthened in height, beyond a top part (h).
 10. The seat as claimed in one of claims 1 to 9, characterized in that a) the movable chain links between the links (410,411) of the link chain (41) and preferably also between the final bottom chain link (411) and the bridging link (42) are formed by hinges (417) in the form of elements positively connected together or film hinges; b) the link chain (41) is provided on the side remote from the seat part (3) with rear stops (414) which, remote from the seat part (3), block the link chain (41) and bridging link (42) from bending to the rear; and c) the link chain (41) may be provided on the side facing the seat part (3) with front stops (413), which block a precurved deformation counter to the load effect, facing the seat part (3), beyond a maximum defined mass.
 11. The seat as claimed in one of claims 1 to 10, characterized in that the mechanism (2) positioned on a lower frame (1): a) when adjusting the backrest (4) between the zero position (R₀) and the inclined position (R_(max)), serves for the synchronous movement of the seat part (3) between a zero inclination (S₀) and a maximum inclination (S_(max)); b) comprises a base part (20), in principle fixedly positioned on the lower frame (1), through which the first rotational axis (D1), which is fixed in principle, extends; c) comprises a seat support (21) supporting the seat part (3) through which a second rotational axis (D2) extends, to which connectors (22) are articulated, on the one hand, which are articulated, on the other hand, to the first rotational axis (D1); and d) has a third rotational axis (D3) extending through the base part (20), to which the seat support (21) is articulated.
 12. The seat as claimed in one of claims 1 to 11, characterized in that a) the backrest connector (43) is fastened to the connectors (22); b) the backrest connector (43) is of two-arm configuration and both arms have in each case a molded part at the ends facing the connectors (22), said molded part (44) being intended for fastening to the respectively associated connector (22); c) at least several links (410,411) of the link chain (41) and optionally also the bridging link (42) are provided with upholstery supports (48), which serve for supporting an upholstered part (49) present on the backrest (4); and the upholstery supports (48): d) are fastened by means of connecting links (480) to the respective link (410,411,42); or e) extend integrally from the respective link (410,411,42).
 13. The seat as claimed in at least one of claims 1 to 12, characterized in that the link chain (41): a) is an integral plastics molded part; or b) is an integral plastics molded part with the upholstery supports (48); or c) is an integral plastics molded part with the upholstery supports (48) and the bridging link (42); or d) is an integral plastics molded part with the upholstery supports (48), the bridging link (42) and the backrest connector (43); and e) the restoring spring for adjusting the backrest (4) into the zero position (R₀) when there is no load effect: ea) is an additional function of the actuating element (47) and a separate traction element may be fixed to the backrest support (40) for reinforcing the restoring function of the actuating element (47), wherein the traction element is fixed between the top link (410) and the bridging link (42), preferably on the rear side of the backrest support (40) remote from the user; or eb) is formed by the hinges (417) between the links (411) and/or by the additional function of the actuating element (47) and/or the separate traction element.
 14. The seat as claimed in at least one of claims 1 to 13, characterized in that a) on the backrest support (40) within the link chain (41): aa) different areas of curvature are formed with a variable precurved deformation with, in principle, variable radii of curvature; and/or ab) different areas of rigidity are formed with variable deformation resistance; and ac) the various areas of curvature with the different areas of rigidity may be configured to be superimposed on one another; and/or b) on the backrest support (40) inside the link chain (41): ba) in the upper region thereof in relation to the lower region a greater precurved deformation is provided in order to provide to the user leaning into the seat, upwards from the shoulder, with a support oriented further toward the user, which may be achieved by different dimensioning and/or variable use of material inside the link chain (41); and bb) the lumbar region in relation to the remaining link chain (41) is formed with a greater deformation resistance, in order to support the user more firmly thereby in said body region.
 15. The seat as claimed in at least one of claims 1 to 14, characterized in that a) a spring, preferably a gas spring (12), is arranged between the lower frame (1) and the mechanism (2) for adjusting the seat height; b) the seat is configured as a swivel chair; c) the base (450) of the adapter arrangement (45) is fastened to the base part (20) of the mechanism (2) or to an extending piston rod of the gas spring (12); d) the backrest support (40) is provided on the side facing the user with an upholstered part (49), which has a lumbar region and at the top may have a top part (h); wherein e) a height-adjustable support element is provided in the lumbar region of the upholstered part (49), and the top part (h) is vertically displaceable. 